Sections 17.2.1 and 17.2.2
give two reasons for using formal methods in HCI: communication
and analysis. These are focused on the sort of mathematical
models found in chapter 17. However, there are other
sort of 'formal' modelling in HCI: dialog notations
are formal models of the syntax of the human­computer
conversation, hierarchical task analysis is a formalisation
of the task structure, some cognitive models are effectively
formal models of the user's mind.

Are communication
and analysis reasons for using these other sorts of
formalism?

Can you think of other reasons why you
would or would not use formalisms?

Try to use these
pros and cons to formulate issues in the choice of appropriate
forms of formal model and analysis.